4 - Central Institute of Brackishwater Aquaculture

National Workshop-cum-Tralning on BioinfWInd~ and Infortnrtlon Manawnt in Aquaculturn
Trait of selection can be of four types i.e.
Production traits
Morphometric traits
Reproductive traits
Quality traits
Among all traits growth rate occupies the top in the list of preference.
5. Role of population size in selection programs
Some of the considerations we often make about genetic improvement assume
we are working with populations of infinite size but in reality we are always
working with population of finite size. If the population size is of finite size then
rate selection response declines, the maximum response is reduced and the
selection limit is reached faster. The inbreeding coefficient increases and that
may have undesirable effects. Rate of inbreeding can be calculated from effective
population size,
F=1/2 Ne after 't' generations F, = 1-(1-(1/2Ne)t
Response per generation R= I h UA
Under inbreeding UA
is reduced by
Aim of any selection is to increase frequency of favorable alleles. Chance of
missing out in favorable alleles increases with reduced Ne. When all are fixed, we
are at limit. It is accepted that rapid inbreeding is more harmful than gradual
mild inbreeding. Incidence of genetic defect increases. For a rate of inbreeding of
- 1% per generation 50 brood fish pairs or more are required.
For analyzing all the data for the selective breeding program different statistical
programs are used. The accuracy of any breeding program depends on the
accuracy of analysis of genetic merit of the individuals. Some of the statistical
programs are described below.
6. Statistical Analytical System (SAS)
SAS software is a combination of a statistical package, a data base management
system and a high level programming language. It can run on a wide variety of
computers and operating systems. SAS programs communicate with the
computer by SAS ststements. It can be used to describe a collection data and
produce a variety of statistical analyses. SAS package has following functions
and advantages.
It is integrated suite of modular products designed to meet a range of focused
information needs.
This software targets and solves industry specific problems.
Allows to easily performing virtually any type of statistical analysis.